The present disclosure is directed to a system and also a method for treating coil springs for cooling. In the fabrication of a coil spring, it is necessary to form the spring by working the metal of the spring at an elevated temperature, and indeed, at a temperature level where the spring is heated to a cherry red glow. The cherry red glow signifies heating to the requisite level so that the spring can then be shaped to a requisite coil size. The spring is bent in the form of a helix. The helix has a diameter which is dependent on the specifications for the spring winding process. In addition to that, the loops or bights which makeup the helix are defined by the spacing which is necessary for the spring to be wound in the spring winding apparatus. There is a small helical gap between adjacent bights or turns of the spring.
The gap bears a substantial relationship to the diameter of the spring and the stock material used in forming the spring. Springs are normally wound of bar stock, but occasionally are wound from non-round stock. In either instance, the stock before winding has a specified cross sectional area which is heated to the very core of the bar stock so that bending to form a multiple loop coil spring provides something of a barrier to cooling. When dipped in cooling oil as part of the spring winding process, the oil must flow through the bights of the spring to the interior. Where the gap between turns is great, the gap readily admits a flow of liquid coolant into the central part of the coil spring. If the spacing is substantial between adjacent loops of the spring, the rate of flow into this area or region is quite high and cooling of the cherry red coil spring is accomplished with uniform exposure on all sides of the bar stock defining the newly made spring. On the other hand, if the gap is relatively narrow or the spring is quite long in comparison with its diameter, there is a significant time lag in the rate of introduction of coolant into the interior of the spring.
This flow to the interior is essential for uniform cooling. By uniform, the cooling that is actually accomplished must cool the different sides or faces of the coil spring at a rate and location enabling the stock to be cooled on all sides substantially and instantaneously. If the number of turns defines a long spring in comparison with the diameter of the spring and if the gap between adjacent bights is relatively narrow, even cooling at the interior regions of the coil spring does not occur. When the cherry red, partly fabricated spring is plunged into a bath of coolant, there is a violent boiling reaction in which bubbles are instantaneously formed. The bubbles are dynamically formed so that there is no cooling at the interior of the coil spring. In the absence of such cooling, the bar stock making up the bights of the fabricated spring are cooled on the exterior side, but they are not cooled at the interior, meaning they are not cooled at the inside face. The term "inside face" will be used hereinbelow to refer to and identify that side of the individual bights which makes up the inside wall of the spring which is typically pressed against a support mandrel shaping the spring. The spring is supported on the winding mandrel thus defining the inside face. It is in that region where cooling is inadequate. Cooling is terribly delayed in contrast with the outer face, meaning the face that is exposed on the exterior of the completed spring. If there is a substantial time lag between cooling at the inside and outer faces, damage is inflicted by this time lag and the spring will not operate effectively or endure vigorous use.
The present disclosure overcomes this problem. A pump operated lance is connected so that a deluge of coolant is interjected against the inside face of the spring. Moreover, this deluge is able to cool from the inside face so that it is quenched at the same rate as the outer face of the coiled spring. This helps cool the helically wound bar stock at a more even rate, especially when speaking of the inside face and outer face. In one aspect of the present disclosure, the violent boiling phenomena which occurs when the spring is first quenched creates a bubble which is shaped approximately equal to or the same as the interior volume of the coiled spring. The present disclosure is directed to a pump and lance support system which delivers flow in that region so that the liquid void resultant from violent boiling is filled. Equally importantly, the lance that supports the coil spring is able to hold the coil spring so that it is positioned in a specified angular relationship to the bath of coolant. The coolant bath is caused to flow in a particular direction within the bath container. This is typically an open top tank in which the coolant quenches the cherry red heated metal spring. There is a directional flow in the tank so that this flow pattern helps fill the cylindrical void that might otherwise occur when quenching occurs.
Considering now certain aspects of the method of the present disclosure, a coil spring is wound to form a number of turns such as 5 to 50 turns (as an example) supported on a mandrel. Moreover, the several turns connect in such a way that liquid cooling at the inside interface is prevented or at least delayed. In particular, the system of the present disclosure helps deliver coolant for quenching to the interior of the coil spring, namely, to that region which is normally a bubble or void, harmful to the product not yet finished. The finished spring has the same form when it is a properly quenched coil spring. Without the method and apparatus set forth by the present disclosure, it has been difficult and typically impossible to obtain properly a fabricated coiled spring.
Summarizing very briefly, the present disclosure sets forth an overhead hoist which has a positive displacement double acting cylinder which extends downwardly toward the bath of coolant. It supports an elongate lance connected with a header and flexible hose to deliver coolant liquid from a pump. Moreover, the coolant is delivered through the lance through a set of holes which adequately deliver the coolant flow volume from the lance. The lance is perforated but not on the full length of the lance. Rather, the lance is perforated along the length of the lance sufficient to position holes inside and parallel to the coil spring. The coil spring is rested on the lance above the tank. The hydraulic cylinder is operated, moving the piston and extending the piston rod. This operates a first switch which starts the pump operating and delivers coolant liquid flow through the hose and into the lance. In addition to that, a second switch is operated which stops downward travel at a location at which the coiled spring is fully submerged in the tank. In this location the coil spring is quenched. It is completely quenched on both the inside face as well as the outer face. Quenching is accomplished by the method of the present disclosure so that heat reduction is accomplished at substantially the same instant on the inside face as well as the outer face. After a required interval, the hydraulic cylinder is operated to retract, raising the lance and thereby permitting the coil spring to be removed from the coolant bath.